Golf balls are well known sporting goods articles that have evolved over the years. Golf balls made prior to the late 1960's typically included a rubber center, a layer of thread rubber windings surrounding the center to form a wound core, and a rubber cover that covered the wound core. The cover was typically formed of a balata rubber (transpolyisoprene, natural or synthetic rubbers). In the late 1960's, DuPont® introduced ionomers under the trade name Surlyn®. Ionomers, such as Surlyn® and related products, such as Iotek® produced by Exxon® Corporation, have been used as a cover material for the majority of golf balls produced since the late 1960's. The use of ionomers in the production of golf ball covers led the way to the development of “two-piece” golf balls, which comprise a solid core and a cover. More recently, thermoplastic and thermoset (castable) polyurethanes have been utilized in the formation of golf ball covers, including golf balls with wound or solid cores. The use of these materials has also led to the proliferation of many multi-layer solid core golf ball constructions wherein two or more layers are applied over a solid core.
Existing two-piece, and multi-layer, golf balls have some drawbacks. All of the various materials used in the construction of golf balls, from wound core constructions through to multi-layer solid core constructions, have varying densities. Accordingly, the mass or weight per unit volume of these materials varies. For example, typically, the materials used to produce the cover layer often possess a greater weight or mass per unit volume than the materials used to produce the core. Additionally, the material composition of most intermediate layers has a density or a weight per unit volume that is different than the density or weight per unit volume of the core and/or the cover layer. If a golf ball is manufactured perfectly, that is if the core or center of a ball is centered exactly, and if the cover layer thickness, and intermediate layer thickness (if applicable), are constant throughout the entire ball, the ball will be “balanced”, and should fly true when struck with a golf club, or should roll true when putted.
However, in the manufacturing of a golf ball, it is very difficult to ensure that a core of the golf ball is exactly and perfectly centered within the ball. Moreover, it is also very difficult to ensure that the thickness of the cover layer, and the thickness of the intermediate layer(s) of multi-piece balls, are uniform and consistent about the periphery of the core. Further, it is also difficult to ensure that the materials comprising the cover layer, and the intermediate layer (if applicable), are properly and sufficiently mixed or homogenized such that the composition and density of the cover layer or intermediate layer is consistent throughout the ball.
Golf balls typically exhibit or possess some degree of manufacturing inconsistency. A two-piece, or multi-piece, golf ball typically includes a core that is not exactly and perfectly centered, a cover layer that does not have a uniform thickness or composition, or an intermediate layer that does not have a uniform thickness or composition. Importantly, these manufacturing inconsistencies can negatively affect the performance of the golf ball.
One common attribute of most golf balls with manufacturing inconsistencies or deficiencies is that such balls will have a heavy spot, or heavy side, and a light spot, or light side. When a golf ball is produced from two or more pieces of varying densities, it is likely that the golf ball will have a light and heavy side. Testing has indicated that if a ball is oriented with the heavy side to one side, erratic behavior in flight properties, and in putting accuracy, can result. Generally, the ball will tend to move toward the direction in which the heavy side is oriented. Such a problem is common in most commercially available golf balls, and is detrimental to the golfer. The imbalance exhibited by the heavy and light spots of a golf ball can cause a putt to veer off line or an iron or driver shot to “hook” or “slice” off of its intended path. Additionally, when a ball is unbalanced, it generally fails to follow a true trajectory and its total flight distance is often negatively affected.
Thus, there is a continuing need for a golf ball that is perfectly balanced and won't depart from its intended flight or roll path due to an off-center core or outer layers of inconsistent thickness. What is needed is a golf ball that does not possess a heavy and light side due to manufacturing inconsistencies and, therefore, flies and putts true. It would be advantageous to develop a true, balanced golf ball that can be readily mass-produced. There is also a need for a golf ball having a cover layer and an intermediate layer (if applicable) of uniform density without areas of uneven material distribution.